Voltage regulator



Jan. 24, 1950 M wl-:NGEL 2,495,301

A. VOLTAGE REGULATOR, lPARTICULARLY FOR FLASH EQUIPMENT FOR PHOTOGRAPHYFiled Oct. 9, 1947 2 Sheets-Sheet l Ill.- j l i r-Lmllmr I A l Jan. 24,1950 1 A. M. wENGl-:L 2,495,301

VOLTAGE REGULATOR, PRTICULARLY FOR FLASH EQUIPMENT FOR PHOTOGRAPHY Filedoet. 9, 1947 l 2 sheets-sheet 2 Patented Jan. 24, 1950 VOLTAGEREGULATOR, PARTICULARLY FOR FLASH EQUIPMENT FOR fPHOTOGRAPHY Arthur M.Wengel, Blooming Grove, Wis., as-

signor to Ray-0-Vac Company, a corporation of WisconsinApplication'October 9, 1947, Serial No. 778.853

15 Claims. l

This invention relates to a voltage regulator, and vmore particularly toa voltage regulator adapted for use in flash equipment for photography.

This application is a continuation in part of my 'copending applicationfor a Voltage regulator, particularly for flash equipment -forphotography, led January 22, 1947, as Serial No. 723,- 494, nowabandoned.

There has been developed in recent years flash equipment for photographywherein the liash bulb is not entirely expended after one operation, butmay be used throughout a great number of dash operations. Flash bulbs ofthis long lasting type often comprise a tube filled with an inert gas,as for example, krypton Vor xenon, and these bulbs usually require asource of high voltage for their operation. In order to provide thishigh voltage a storage condenser may be used in the conventional manner,and this condenser may be charged from a low original source of voltageby means of a step-up transformer or by other means well known to theart.

In utilizing this type of equipment it has heretofore been known to usea relatively inexhaustible supply of current for the original voltagesource, as for example conventional commercial 60 cycle 110 voltalternating current. Obviously the use of this current embodieslimitations on the portability of the equipment, since the equipment isonly usable when there is such a source of current available.

It has also been known to use storage batteries, as for example,conventional automobile leadacid type batteries, as the original sourceof voltage, `and to convert the direct current from the battery into apulsating current by means of a vibrator or other means, and then tostep-up the battery voltage to desired values by means of a transformeror other means. Several disadvantages are inherent in such a system, ior in the rst place the storage batteries used are heavy and bulky andprovide limitations onl the portability of the equipment. Also thesource of current obtainable from vsuch a battery is not inexhaustibleand it has been necessary frequently to charge the batteries, therebyentailing the use of additional apparatus. Furthermore such bat terieshave not been completely reliable even over sho-rt periods of use, forthe voltage step-up reu quired is so great that a very small variationin the output voltage of the battery may result in a very greatvariation in the voltage applied to the flash bulb, thereby resulting inunreliable and unstable operation of the flash equipment.

It has long 'been apparent that the use of dry cell batteries as theoriginal source of voltage in such equipment would be desirable becauseof the relative compactness, lightness and cheapness of dry cellbatteries, but prior to my invention 'the use of such dry cells in'practical photographic work, as for example use by a pressphotographer, has not been feasible because as 'pointed vout above, evena very small change in the battery voltage resulted in a great change ofvoltage being applied to the iiash bulb. For example, in one practicalphotographic iiash device wherein the original 6 volt battery` voltage"is 'stepped up to approximately 2800 volts to apply to the flash bulb,a .1 volt change 'in the battery results in a 50 volt change across the'storage condenser which acts as the power source for the iia'sh bulb,so that any appreciable voltage change in the battery results in veryunreliable and unstable operation of the iiash equipment. n

Prior to my invention no voltage regulating apparatus has been knownwhich wouldy satisfactorily regulate the voltage across 'the storagecondenser despite even slight variations in the voltage of the batteryor other original voltage source, and for this reason previous portableflashers have used storagebatteries despite the inefficiency andinconvenience voccasioned by their use. vOrdinarily voltage regulatingtubes or glow lamps are not capable of operating under the high voltageconditions found in the circuits utilized in such flashers where 'thevoltage may approach 3,000 volts. While the 'thyraton type Iof tubemight be utilized to provide such voltage regulation, prior to myinvention these tubes have not been used because the high voltagesinvolved require that a special high voltage tube be developed, ofundesirable size, and furthermore when using such a tube it is necessaryto heat "or otherwise energize a iilament, thereby causing an'additional drain on the battery or other rsource of current.

I have developed 'and am here disclosing and claiming voltage regulatingapparatus particularly adapted k'for use in vflash equipment iorphotography, this apparatus permitting the use of ordinary dry cells, asfor example a pair of -6 volt conventional electric lantern batteriesconnected in parallel, or flashlight 4cells so con nected as to provide6 volts (preferably eight cells in series-parallel) as the originalsource of voltage. My apparatus has given satisfactory ref sults withsuch batteries for as long 'as nine hours of continuous operation, atwhich time the voltage of the battery dropped from 6 to 3.6 volts.

Photographic flashers equipped with my improved voltage regulator are,therefore, in addition to being truly portable without the limitationsimposed by a heavy and bulky storage battery or the necessity of havinga commercial source of current available, capable of greatly improvedand more enicient operation over any similar equipment heretofore known.

Other features of my invention will be apparent from the followingdetailed description and from the drawings in which:

Fig. l is a schematic diagram of photographic flash equipment includingone form of my invention; and

Fig. 2 is a schematic diagram of photographic flash equipment includinganother form of my invention.

Referring to Fig. l, an original source of voltage is illustrated as abattery l0, which may be a pair of conventional 6 volt electric lanterndry f cells connected in parallel. One terminal of this source 0ivoltage is. connected to ground and the other terminal is connectedthrough a vibrator which is adapted to convert the direct current fromthe battery into a pulsating current so that the voltage of the batterymay be stepped up to -a desired value. This vibrator comprises an in-`ductance or operating coil li, a switch l2 which may be of thevibrating reed type, and a condenser l3 connected across the inductanceand the switch. As a result of the periodic opening and closing of theswitch l2 the direct current from the battery is converted into aunidirectional pulsing current which ows through the primary iilc oi atransformer' ill when a switch I5 is closed and a safety swi'ch '.t isin the position illustrated in the drawing.

The pulsating direct current llowing through the primary ida is steppedup to a desired high voltage and converted into alternating current inthe secondary Mb of the transformer, in one practical apparatus which Ihave constructed the step up ratio of this transformer beingapproximately 470 to l so that the voltage in the secondary circuit isapproximately 2800 volts when the voltage of the battery l0 is 6 volts.The high voltage circuit includes in series a limiting resistor ll whichmay have a value of 10,000 ohms and a rectifier which is hereillustrated as a diode I8 which may be of tube type No. 1654 and has itsplate connected to the high voltage side of the circuit and its cathodeconnected to ground. Heater voltage for this diode is furnished from asource i0 which may comprise a 1.5 volt conventional flash light cell,the voltage from this cell being selectively applied to the filament ofthe tube by means of a switch 20. It will be understood, of course, thata cold cathode or other suitable rectiiier may be used. The circuit alsoincludes an. impedance across which desired voltage may be developed.While any desired impedance across which a voltage may be developed forcharging the storage condenser may be used, as a resistance or aninductance, in the photographic flash apparatus illustrated the otherend of the transformer secondary is shown as being connected directly toone Iplate of a storage condenser 2l, and the other plate of thiscondenser is connected to ground. This condenser may have a capacity of25 microfarads, and should have a voltage rating in excess of thehighest voltage applied across, it, as for example, a rating of at least3,000 Volts in the example mentioned heretofore.

In order to guard the safety of operating per- Il (l sonnel, oneterminal of the safety switch l5 is connected to the high voltage side othe transformer secondary and the storage condenser through a resistor22 which may have a value oi 5,000 ohms, and it will be readily seenthat when this switch I8 is thrown to the position other than that shownin the drawing (which may be effected automatically by movement of thelid of the case for the unit, or the like) the circuit of the battery l0will be opened and any charge on the condenser 2l will rapidly leak offto ground through the resistor 22.

The storage condenser 2l acts as a source of voltage for the ilash lamp23 which may be of the continuously usable type having an inert gastherein as, for example, krypton or xenon. A connection is made from thehigh voltage side of the condenser 2l to the lamp circuit through acable 24, it being understood that this cable may be of any desiredlength. y

The ilash bulb 23 has its own circuit associated with it, and since thiscircuit is known to the art it will be only briefly described here ascomprising a resistor 25 which may have a value oi 45 rnegohms, atransformer 26, a resistance-capacity network comprising a condenser 27which may have a capacity of .5 microfarad and a voltage rating of 600volts and resistor 28 connected in parallel therewith, this resistorhaving a value of 5 megohms. A switch 29 which may be of the push buttontype, or of a conventional type snap switch, is closed when it isdesired to flash the bulb, and the bulb and circuit arrangements aresuch that when the circuit is Closed the condenser ZI rapidly dischargesthrough the lamp, and a ilash lasting approximately 1/1o,coo of a secondoccurs. During this flash period approximately 500 kilovolt amperes ofenergy are utilized, and the voltage across the condenser 2l drops toabout 200 or 300 volts above ground, from which point the condenseragain begins to charge.

I have devised a voltage regulating circuit which is particularlyadapted to be utilized with photographic ilash equipment, and which iscapable of F maintaining the voltage across the condenser 2l constantwithin close limits despite relatively great variations in the originalvoltage from the battery il). My new voltage regulator comprises novelcircuit arrangements associated with a tube connected in shunt with theimpedance 2l, said tube being arranged to pass current whenever a.predetermined desired voltage is developed across said impedance, saidcircuit arrangements providing a means for cutting off said current flowvery shortly after its initiation. The tube illustrated in the drawingat 30 may comprise a conventional so-called Amglo cold light lamp suchfor example as Amglo lamp type `-lo. 'IGC-LR. These tubes aremanufactured by Amglo Corporation and since they are commerciallyobtainable, their` structure will not be described in detail here,reference being had to patents issued to Andrew F. Henninger, Jr., andGeorge D. Henninger, in particular U. S. Patent No. 2,217,315 issuedOctober 8, 1940, U. S. Patent No. 2,273,520 issued February 17, 1942,and U. S. Patent No. 2,281,579 issued May 5, 1942.

Briefly, the tube is of the cold cathode type and comprises an envelopecontaining a gas such as mercury. Within the tube are at least twoelectrodes, the tube illustrated in the drawing having an anode 30a andcathode electrodes Elib and 39o, and a distinguishing, characteristic ofthis tube is that means are provided within the tube for causing anyspace current flowing between two proper operation of the flash lamp 23.This efcient resuflt is obtained despite the fact that only single waverectification is provided in the high voltage circuit, and the desiredvoltage is maintained even when the voltage from the battery l drops aslow as 3.3 volts under load or 4 volts open circuit. When this occurs,of course, the life of the battery is practically over, but until suchbattery is almost completely used up the only difference in theoperation of my circuit is that a longer charging time is required toobtain the 2,000 volts across the condenser 2|. When the battery voltageis down to 3.8 volts the charging time may be approximately 60 seconds,and the flashing across the tube 30 after the condenser is chargedcannot be repeated as rapidly as with fresh batteries, but thephotographic effeet of the flash is still substantially the same.

I have found that when a fresh 6 volt battery is used for the source I0,the current drain is about 1.9 amperes at the start of the chargingcycle and 1.4 amperes after the condenser 2l reaches a charge of 2,000volts. When the battery voltage is down to 3.6 volts, which may ocourafter about nine hours of continuous use when two 6 volt conventionalelectric lantern dry cell batteries connected in parallel are used, thecurrent drain is about 1.1 amperes at the start of the charging cycleand about .42 ampere when the condenser is charged. Even with such an fexhausted battery I have found that my novel voltage regulator circuitmaintains the voltage across the condenser at approximately 1,950 volts.

Fig. 2 comprises a preferred embodiment of my invention, and in saidfigure circuit components which are similar to those of Fig. 1 aredesignated by reference characters 40 higher than the characters used inFig. l.

In Fig. 2 a battery 50 comprises a source of voltage, one terminal ofthe battery being connected to ground and the other terminal beingconnected through a vibrator comprising an inductance i, a switch 52 anda condenser 53 to the primary 54a of a step-up transformer 54. As inFig. 1 an on-off switch 55 controls the battery circuit when the movableelement of a safety switch 5S is in the position shown in the draw- Thehigh voltage circuit includes the transformer secondary 54h, a limitingresistor 51 and a diode rectifier 58, the filament of this diode beingsupplied with heating current from a battery 59 through a switch 60. Animpedance comprising a storage condenser 6I is connected between thehigh voltage side of the secondary and ground, and a bleeder resistor 62is in the lead from the high voltage side of the condenser 6| and thetransformer secondary to the safety switch 56.

A cable 64 leads from the condenser 6I to a flash lamp G3 and itsassociated circuit. As in the embodiment earlier described, this circuitcomprises a resistor E5, a transformer 66, a resistance-capacity network67-68 and an oper-` ating switch 69.

The voltage regulating apparatus comprises a tube which has at least twoelectrodes therein and which may be of the same type as the tube ofFig. 1. Said tube is connected in shunt with the impedance 0| and isarranged to pass current whenever a predetermined desired voltage isdeveloped across said impedance, the circuit arrangements associatedwith the tube providing a means for cutting off said current flow veryshortly after it is initiated. As in the apparatus of Fig. 1, this tubemay comprise a conventional gas lled device having therein a tortuoustube cf glass or other insulating material surrounding the anode andcoiled in such manner that the discharge between the anode and a cathodefollows the tortuous path deiined by the glass tube and travels adistance substantially longer than the straight line distance betweensaid electrodes. As in the apparatus of Fig. l, the tube 'l0 isinversely connected in the circuit, its anode 10a being connected to thenegative side of the high voltage supply through the resistors 15a andlh, and one of its cathodes l'c being connected to the positive orgrounded side of the high voltage supply. The resistor 15a may have avalue of 400,000 ohms, and the resistor 15b may have a value of 150,000ohms. A condenser 14, which may have a value of .005 microfarad and avoltage rating of 2500 volts is connected between the mid-point ofresistors 15a and 15b and the other cathode 10b oi the tube l0; and acondenser 16, which may have a value of .0005 microfarad and a voltagerating of 2500 volts is connected between the cathode 70o and the anode10a.

This voltage regulating circuit comprises two relaxation oscillators,one including the condenser 'l0 and the tube electrodes 10a and 10cthrough the tortuous electron path in the tube, and the other includingthe condenser "M and the electrodes 10b and 10c. Because of the inversevoltage characteristics of the tube and because ci the relatively longgap between the electrodes 70a and 'lflc caused by the tortuous path inthe tube, the relaxation oscillator comprising the condenser 16 and theelectrodes 10a. and 10c operates only when a predetermined. relativelyhigh voltage exists across the electrodes 10a and 10c, as for example avoltage in the neighborhood of 2400 volts. Since the condenser 16 is ofa comparatively small value, the time constant of this relaxationoscillator is relatively small, and this circuit will oscillate at ahigh frequency.

The other relaxation oscillator comprises the condenser l!) and theelectrodes 10b and 10c. The electron path between these electrodesfollows a straight line and is relatively short, normally in theneighborhood of one-quarter inch, so that the operating voltage of thiscircuit is only about 1400 volts, and since the condenser 'M is verylarge as compared with the condenser l0 the frequency of oscillation ofthis latter circuit is lower than is the frequency of oscillation of thecircuit including the condenser l. As will be apparent from the abovedescription, the difference between the two striking voltages of therespective oscillate-1' circuits is approximately 1,000 volts, and thisis the variation that the voltage regulator must handle.

In operation, as the voltage across the storage condenser 6l isgradually building up, a discharge occurs between the electrodes '10band 10c when a potential difference of 1400 volts across the condenser0l is reached, and the relaxation oscillator including the condenser'.'4 and said electrodes operates at its relatively low frequency. Thesmall size of condenser 'I4 limits the quantity or" current during eachcycle of oscillation, and consequently the voltage across condenser 6!continues to build up faster than it can be dissipated by thisrelatively low frequency relaxation oscillator'. When the voltage acrossthe storage condenser has increased to about 2400 volts, and at aninstant when the relaxation oscillator including condenser 14 is notoperating,

a discharge -occurs between the electrodes 10a and loe and the otherrelaxation oscillator including these electrodesA and the condenser I6goes into operation.

`As pointed. out earl-ier., this last mentioned re laxationvoscillator-has'- a. .higher operating frequency than the iirst mentionedvoscillator .so it operates ior .a ,plurality of cycles bef-ore thevoltage across condenser le rises. to a .high enough level to triggerthe Vlower frequency oscillator. However, at .an .instant .betweencycles of .the high frequency oscillator the .low frequency oscillatoragain vfires to stop operation of the high frequency oscillator. It willbe vseen that if the high frequency .oscillator res at approximately thevol-t'- age which. rit is desired to maintain across Ythe storage.condenser 6l, a voltage will never build u'p across said storagecondenser .in excess of this value, andv it will also be seen that ifthe .low .-frequency oscillator operates at vthe proper frequency tolstop the high frequency oscillator beforel the -voltage'across thecondenser El has been dissipated by .more .thanaiew volts, said voltageacross the storage condenser will never fall below a.` predetermined-minimum, .but will remain almost constant. When the Vlow frequencyoscil lator hres it drops the voltage across the circuit components-ofthe other, and stops its operation until the .voltage has again built upacross the condenser to a point initiating resumption of operationofgthislatter oscillator effect.

While the circuit. of Eig. '2 will operate with most l'tubes.without themodification described .in connection .with Fig. 1',.I"have 'found thatwith certain tubes the inversel striking voltage is much than is normalwith .most tubes. In this event the tube maybe modied by adding -a.small capacity comprising a condenser ll, a leadV l2 and avwashermember 73. Asin the modification 4described in connection with Fig. l,'it is not necessary to utilize an actual physical condenser'but thecapacitive effect may .be obtained by aflixing a washer 1.3 to theenveloperof the tube lll and wrapping one end of a lead 'I2 whichextends .from the washer around the resistor '5l or some other .point inthe circuit .having a voltage differential with respect to one of theelectrodes in the tube l0.

In constructing my voltage regulating circuit 'foruse with highpotentials, .as 2G00 or 24Go volts, I have found that utilizing theinverse voltage characteristics of the tube l is important, for if thepolarity of the circuit is reversed all regulation stops and the tubewill fire andholduntil the voltage falls to a very low value. However,by connecting the tube inversely in the circuit a small, inexpensive andreadily portable tube may be usedto obtain the same high voltageoperation for which a very large tube would otherwise .be necessary.Furthermore, in constructing. the circuit I have found' that the valueof the condenser 16 is very critical. Since the value of this condenserdetermines the time constant and the frequency ofthe yhigh 'frequency'relaxation oscillator circuit, if this condenser is omitted noregulation takes place; if it is made too small, the frequency of itsrelaxation oscillator circuit is too high andthetuledoesfnotregulatewell, but will fire and hold until the voltage drops to a very lowvalue. If the condenser is made too large, the .frequency of. theoscillator is too low, the. circuit llires slowly', and too much voltageis dissipated during each relaxation cycle.' In either of' the lattercases the current through the tube is interrupted for too long or tooshort a period of time and the voltage is crrespondinglyralsed orloweredl in an undesired manner in proportion to the on and oli timeratios.

While I have shown and described certain em-4 5 bodimcnts of myinvention, it is to be understood that it is capable of manymodifications. Changes, therefore, in the construction and arrangementmay be made without departing from the spirit and scope of the4invention as di'sclotedl in theappended claims.

I-claim-z- Lnpparatus of the character described, .including.: y acircuit including an impedance; a source of voltage for developing apotential .across said impedance; a gaseous voltage regulating 'tube'connected in .shunt with at least part o'f said impedance, said tubehaving atleast two electrodes therein; and a low value capacityconnection btween a pointV in said circuithaving a voltage differentialwith respect to one of said electrodes and said tube for providing anionizing effect on the gas within said tube.

vl Apparatus of the character described, 'including: a circuit includingan impedance; a source .of voltage for developing a'p'otential acrosssaid impedance; a vgaseous voltage regulating tube connected in shuntwith at least part of said 'impedance, said v.tube having an anodeelectrode and at least one cathode electrode therein and having thereina tortuous Velectron e path for any space current iiowing between saidanode and cathode electrodes, said path being very substantially longer'than Athe straight line distance between said two electrodes; anda lowvalue capacity' con# nection between said circuit and said tubeforproviding an ionizing -eflect, onl the ygasjwithin said tube. A

3. Apparatus ofthe `ozhvarz'icter described, including: an impedance; asource of voltagedor developing a potential' across said impedance;avolt'age regulating tube .connected nshunt with at least vpart of saidimpedance, said tube having an anode electrode and Vatleastv one cathodeelectrode therein; and a resistance-capacity net- 45, work connected inseries with one o'fs'alid elec trodes.

4. Apparatus of the character described, -iiclii'ding: a circuitincluding an impedance; a source of' voltage for developing a potentialVin said circuitv across said impedance; a voltage regulating gaseoustube connected in shunt with at .least part of said impedance, Vsaidtube having an anode electrode and at least one cathode electrodetherein; a capacitive connection between two electrodes of said tube; alow value capacity connection between a' point in said circuit having avoltage differential with respect to one of said electrodes and saidtube for oro-A viding an ionizing effect on the gas within said 60 tube;and a resistance-capacity network having a short time constant and beingconnected iii series with said anode.

5a .Apparatus of the character claimed inclaim 4, wherein saidresistance-capacity netwoik'has a time .constant not in excess vofoneonefthou'- sandth `olf a second.- a

6. Apparatus ofthe character claimed in .claim 1'... wherein said lowvalue capacity connection includes a conducting member located closelyadjacent one of the electrodes in said tube.

i7. In hash illuminating apparatus having a .hash lamp, .a condenser forenergizing the lamp, and voltage vsupply means .for charging thecondenser, voltage regulating means including: .a 76 discharge tubeconnected in shunt with said 11 condenser, said tube having an anode andat least one cathode electrode therein; a capacitive connection betweenvtwo electrodes of said tube; and means comprising a low value capacityconnection between one of said electrodes and a point in said voltagesupply means having a voltage diierential with respect to one of saidelectrodes, for providing an 'ionizing eiect on the gas within saidtube.

8. In h illuminating apparatus having.a iiash lamp, a condenser forenergizing'the lamp, and voltage supply means for charging thecondenser, voltage regulating means including: a discharge tubeconnected in shunt with said condenser, said tube having an anode'and atleastone cathodel electrode therein; and a resistance-capacity networkconnected in series with one of said electrodes.

f 9. In flash illuminating apparatus having a il-ash lamp, a 'condenserfor energizing'the lamp, and voltage supply means for charging theoondenser, voltage regulating means including: a gaseous tube connectedin shunt with said condenser, said tube having an anode and at least onecathode electrode therein; a capacitive connection between saidanode andone cathode electrode; means comprising a low Value capacity connectionbetween apoint in said voltage supply means having a voltage diierentialwith respect to one of said electrodes and one of said f electrodes forproviding an ionizing elect on the gas within the tube; and aresistance-capacity network connected in series with said anode, saidnetwork having a short time constant. i

,"10. Voltage regulating apparatus ofthe character described, including:a tube having an anode and at least one cathode electrode; a capacitiveconnection betweenlsaidanode and at least one cathode of said tube; aconductingmember located closely adjacent `an electrode inpsaid tube andadapted -to provide a 10W` valuev capacity connection to said electrode;and a current limiting device connected in series with the anode of saidtube.

11. Apparatus of the character described, including: an impedance; asource of voltage for developing a potential across said impedance; atube connected in shunt with at least part of said impedance; a firstrelaxation oscillator circuit including said tube, said oscillatorcircuit being adapted to operate when a predetermined desired voltage isdeveloped across said impedance; and a second relaxation oscillatorcircuit including said tube, said second oscillator circuit beingadapted to operate to terminate operation of said rst oscillator circuitvery shortly after operation of said rst oscillator circuit isinitiated.

12. Apparatus of the character described, including: an impedance; asource of voltage for developing 'a potential across said impedance; atube connected in shunt with at least part of said impedance, said tubehaving at least three electrodes therein; a circuit comprising a rstrelaxation oscillator and including a pair of said electrodes, saidoscillator being adapted to operate when a predetermined desired voltageis developed across said impedance; and a circuit comprising a secondrelaxation oscillator and including another pair of said electrodes,said second oscillator being adapted to operate to terminate operationof said first oscillator very shortly after operation of said irstoscillator is initiated.

13. Apparatus of the character described, including: an impedance; asource of voltage for developing a potential across said impedance; agaseous discharge tube connected in shunt with at least part of saidimpedance, said tube having at least three electrodes therein; a circuitcomprising a first relaxation oscillator and including a pair of saidelectrodes, said oscillator being adapted to operate when apredetermined desired voltage is developed across said impedance; and acircuit comprising a second relaxation oscillator and including anotherpair of said electrodes, said second oscillator being adapted to operateto terminate operation of said iirst oscillator very shortly afteroperation of said rst oscillator is initiated, said circuit arrangementsbeing such that said second oscillator operates at a lower voltage andat a lower frequency than said iirst oscillator.

14. Apparatus of the character described, including: a circuit includingan impedance; a source of voltage for developing a potential across saidimpedance; a gaseous voltage regulating tube connected in shunt with atleast part of said impedance, said tube having an anode electrode and atleast one Acathode electrode therein and having therein a tortuouselectron path for any space current owing between said anode and cathodeelectrodes, said path being very substantially longer than the straightline distance between said two electrodes; connections between'an anodeelectrode of said tube and the negative side of said source; connectionsbetweenL a cathode electrode of said tube and the positive side of saidsource; and a low value capacity connection' between said circuit andsaid tube for providing an ionizing eect on the gas within said tube. v

15. Apparatus of the character described, including: an impedance;l asource of voltage for developing a potential across said impedance; agaseous discharge tube connected in shunt with at least part of saidimpedance, said tube having anode and cathode electrodes therein;connections between an anode electrode of said tube and the negativeside of said source; connections between a cathode electrode of saidtube and the positive side of said source; a circuit comprising a firstrelaxation oscillator and including a pair of said electrodes, saidoscillator being adapted to operate when a predetermined desired voltageis developed across said impedance; and a circuit comprising a secondrelaxation oscillator and including another pair of said electrodes,said second oscillator being adapted to operate to terminate operationof said rst oscillator very shortly after operation of said rstoscillator is initiated, said circuit arrangements being such that saidsecond oscillator operates at a lower Voltage and at a lower frequencythan said rst oscillator.

ARTHUR M. WENGEL.

REFERENCES CITED The following references are oi record in the levofthis patent:

UNTTED STATES PATENTS

